In the last decade, projection display technology has undergone a technological revolution. For example, projectors are now able to display images with very high spatial resolution and dynamic range. At the same time, projectors have become highly efficient in terms of both size and power consumption, while improved designs have resulted in substantial price reductions that have enabled greater usage for both business and consumer purposes. As a result of these advances, projectors have become somewhat ubiquitous, and are becoming more of an integral part of our everyday lives.
Several different types of display systems have been developed that use one or more projectors as the basic building blocks. For example, images produced by an array of projectors have been tiled to create large, ideally seamless displays having high resolution. Sets of projectors have also been used to project onto large surrounding surfaces to create immersive environments. Additionally, for example, multiple registered projectors have been used to project onto the same surface in order to display an image that optically combines several component images. This approach has been used to produce high quality images, e.g., images with regions having different depths of field, and images whose reflection components (specular reflection and diffuse reflection) are computed in parallel. Projectors have also be used to make a Lambertian white object appear to be one with that includes albedo variations, and to introduce transparency effects to the appearance of an object or to make an object appear reflective.
Each of the above types of display systems rely on some prior information about the projectors being used and the surfaces onto which they project. In many cases, for example, the geometric mapping between one or more projectors and a display surface being projected onto must be known. Additionally, for example, the photometric properties of the projectors must be calibrated and accounted for when displaying multiple, over-lapping images onto a display surface. One way to solve these geometric and photometric calibration problems has been to incorporate one or more cameras into the display systems. These cameras not only provide measurements needed for calibration, but can also be used to make the projection systems more intelligent and adaptive. For example, a camera can be used with multiple projectors to eliminate the casting of shadows on the projection surface. It has also been known to use a camera as a user interface component to enable a user to interact with the projected image. A camera can also be used to find a surface patch with constant reflectivity that can then be used as the display surface of the projector.
Despite the above advances, the versatility of current projector-based display systems remains significantly limited. For example, current projector-based display systems lack the ability to control the appearance of a surface having variations in its color. Additionally, for example, current projector-based display systems are limited by the requirement that a high quality surface be used in order to ensure a high quality image output. This requirement generally precludes the use of arbitrary surfaces, because such surfaces cannot be relied on to be highly reflective and white as is typically necessary to obtain optimal results with conventional projection systems. Rather, an arbitrary surface is extremely likely to have spatially varying photometric properties resulting from non-uniformity in color (e.g., when the surface being projected onto is a brick wall, a painting or poster on a flat wall, tiles of a ceiling, a portion of a grainy wooden door, etc.) and/or imperfections (e.g., paint imperfections, holes, nails, etc.). When an image is projected onto such an arbitrary surface in a conventional projection system, the image output is modulated by the spatially varying reflectance properties of the surface, and the image output becomes undesirable to human perception. Moreover, while it may be incorrectly assumed that this limitation can be remedied using a projector of high power (i.e., brightness), increasing the brightness does not change the proportion of the modulation.
Accordingly, it is desirable to provide projection methods and systems that are able to project their images onto virtually any surface (e.g., walls, doors, drapes, ceilings, etc.) while improving the photometric quality of their output. Additionally, it is desirable to provide methods and systems that are able to project images onto a surface in order to control the appearance of the surface.